Film formation method

Abstract

This film formation method comprises: disposing, in a chamber (12), a target (20) comprising yttrium and a substrate (W) that is an object on which a film is to be formed; introducing at least oxygen into the chamber (12); applying a prescribed bias voltage to the substrate (W); evaporating the surface of the target (20) in oxygen to form an yttrium oxide film on the substrate (W); and setting the oxygen partial pressure in the chamber (12) during the evaporation so as to be a pressure of less than 0.4 Pa, and setting an O / Y ratio, which is the ratio of oxygen to yttrium in the yttrium oxide film on the substrate (W), so as to be 1.5 or less.

Description

Film forming method

[0001] The present invention relates to a film forming method for forming a film having excellent plasma resistance on the surface of a substrate.

[0002] Conventionally, there has been a demand for materials with excellent plasma resistance for components used in environments exposed to plasma, such as semiconductor manufacturing equipment. In Patent Document 1, in order to obtain such materials, yttrium oxide (Y ２ O ３ In this technique, a Y ２ O ３ By plasma spraying using powder as a raw material, a film of yttrium oxide is formed on the surface of components where damage by plasma is a problem.

[0003] Meanwhile, in recent years, the formation of an yttrium oxide film on a substrate by a vacuum deposition method (PVD method: Physical Vapor Deposition) has been investigated. Since such a PVD method uses ionized materials to form a film on a substrate, it is possible to form a denser coating compared to thermal spraying methods, which may have defects in the film. It is generally known that in the PVD method, a certain percentage of the evaporated atoms are ionized and become ions. Therefore, by applying a voltage (bias) to the substrate on which the film is to be formed and changing the incident ion energy, the density and film properties (crystal structure and mechanical properties) of the coating can be controlled.

[0004] Among PVD methods, the AIP (arc ion plating) method is a film formation method based on the evaporation and ionization of a cathode material by vacuum arc discharge under conditions of high current (tens to hundreds of amperes) and low voltage. In this case, when forming a film of an insulating material such as an oxide, reactive film formation is required using a metal target in an oxygen-containing atmosphere. Since the cathode discharge surface is oxidized during this process, if there are areas on the cathode surface where arc discharge does not occur, oxides will accumulate in those areas, and the expansion of those areas will likely make it difficult to sustain the discharge. To solve this problem, Patent Document 2 discloses that stable discharge can be achieved by using an evaporation source with a weak magnetic field of 3 to 50 gauss. Patent Document 3 discloses using this method to apply bipolar pulses to form oxides under pure oxygen conditions. The same document also discloses the formation of films of oxides containing Zr, Cr, Mo, and Al, Si, Fe, Co, Ni, and Y by superimposing a high-current pulse arc on a direct current.

[0005] Japanese Patent Publication No. 2001-164354 Japanese Patent No. 5306198 Japanese Patent No. 5877147

[0006] The present inventors have used the method disclosed in Patent Document 2 to obtain Y ２ O ３ However, it was found that there was a problem that an oxide formed on the target surface during long-term discharge, and discharge eventually became impossible. Furthermore, the high-current pulse arc described in Patent Document 3 has a problem that the power supply system is more complex and expensive than a normal DC power supply, making it difficult to apply industrially.

[0007] An object of the present invention is to provide a film formation method that can stably maintain discharge during film formation when stably forming an electrically conductive yttrium oxide film on a substrate using an arc ion plating method.

[0008] In order to achieve the above object, the inventors of the present application have conducted extensive experiments to form a conductive yttrium oxide film, and as a result have discovered a new film formation method.

[0009] A film formation method according to the present invention is a film formation method for forming an yttrium oxide film on a substrate, which is the object of film formation, by an arc ion plating method, and includes the steps of: placing a target made of yttrium and the substrate in a chamber; introducing at least oxygen into the chamber; applying a predetermined bias voltage to the substrate; evaporating the surface of the target in oxygen to form an yttrium oxide film on the substrate; and setting the oxygen partial pressure in the chamber during the evaporation to a pressure less than 0.4 Pa such that the O / Y ratio, which is the ratio of oxygen to yttrium in the yttrium oxide film on the substrate, is 1.5 or less.

[0010] FIG. 1 is a schematic diagram showing the general configuration of a film formation apparatus for performing a film formation method according to one embodiment of the present invention. FIG. 2 is a graph showing the relationship between the O / Y ratio, which is the ratio of oxygen to yttrium in the yttrium oxide film on the substrate, and the electrical resistance of the yttrium oxide film in an example of the present invention. FIG. 3 is a graph showing the relationship between the oxygen flow rate and the oxygen partial pressure in an example of the present invention. FIG. 4 is a graph showing the relationship between the oxygen partial pressure and the discharge voltage in an example of the present invention. FIG. 5 is a graph showing the relationship between the oxygen partial pressure and the discharge voltage in an example of the present invention. FIG. 6 is a graph showing the surface roughness of yttrium oxide films formed by changing the oxygen partial pressure in an example of the present invention. FIG. 7 is a graph showing the change in oxygen partial pressure during long-term discharge in an example of the present invention. FIG. 8 is a graph showing the change in discharge voltage during long-term discharge in an example of the present invention. FIG. 9 is a graph showing the O / Y ratio of yttrium oxide films formed by changing the oxygen partial pressure in an example of the present invention.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the general configuration of a film formation apparatus 10 for performing a film formation method according to an embodiment of the present invention. The film formation method according to an embodiment of the present invention is a method for forming a film having excellent plasma resistance on the surface of a substrate.

[0012] 1 shows an example of a film formation apparatus for carrying out the film formation method according to the embodiment of the present invention, and the film formation apparatus for carrying out the film formation method is not limited to that shown in Fig. 1. This film formation apparatus 1 is an apparatus that uses a physical vapor deposition (PVD) method to form a film on the surface of a workpiece W (substrate) placed in a vacuum chamber 2. This film formation apparatus 1 includes an AIP apparatus that forms a film using an arc ion plating method, a sputtering apparatus that forms a film using a sputtering method, and the like.

[0013] The film formation apparatus 10 is an arc ion plating apparatus and includes a vacuum chamber 12, a rotary table 14, a plurality of substrate holders 16, a bias power supply 18, a target 20 as an evaporation source, an arc power supply 22, a heater 24, an argon tank 30, an oxygen tank 32, a vacuum pump P, and a controller 50.

[0014] The vacuum chamber 12 accommodates a turntable 14 and a plurality of substrate holders 16 arranged on the turntable 14. The interior of the vacuum chamber 12 (i.e., the space accommodating the turntable 14 and the plurality of substrate holders 16) is maintained in a vacuum or near-vacuum state by a vacuum pump P during various processes including the film formation process. The vacuum chamber 12 is provided with a gas inlet 12A and an exhaust outlet 12B.

[0015] The turntable 14 has a disk shape with a centerline extending in the vertical direction in Fig. 1 . The turntable 14 is disposed within the vacuum chamber 12. During the film formation process, the turntable 14 rotates around its centerline while supporting a plurality of substrate holders 16. The turntable 14 may further include a turntable on which each of the plurality of substrate holders 16 is individually disposed so that each of the plurality of substrate holders 16 can rotate on its own axis. The number of substrate holders 16 is not limited to two as shown in Fig. 1 .

[0016] Each of the plurality of substrate holders 16 supports a workpiece W on which a film is to be formed.

[0017] In this embodiment, the workpieces W are arranged on the outer peripheral surface of the substrate holder 16. Note that only a portion of the workpieces W is shown in FIG.

[0018] In this embodiment, the workpiece W is made of an A6061 alloy (Al alloy) and is a square plate piece measuring 20 mm x 20 mm. However, the material and shape of the workpiece W are not limited to this.

[0019] Each of the substrate holders 16 is made of a conductive material, such as stainless steel.

[0020] The plurality of substrate holders 16 are arranged at equal intervals in the circumferential direction of the turntable 14. In this state, the center line of each of the plurality of substrate holders 16 is parallel to the center line of the turntable 14.

[0021] The bias power supply 18 applies a negative bias voltage to each of the plurality of substrate holders 16 via the rotary table 14. In this embodiment, the bias power supply 18 intermittently applies the negative bias voltage to each of the plurality of substrate holders 16. In other words, the bias power supply 18 is a pulse power supply. When the resistance of the coating formed on the workpiece W is relatively high, applying a DC bias as the bias voltage may cause a problem of charge accumulation (charge-up) due to incident ions. On the other hand, by applying a pulse voltage as the bias voltage as in this embodiment, this problem can be prevented even when the resistance of the coating formed on the workpiece W is relatively high. More specifically, the charge-up problem can be prevented by switching the bias between the negative side and 0 V or the positive side as the pulse voltage on the order of μS or mS.

[0022] Note that the bias power supply 18 does not apply a bias when it is not applying a negative bias voltage during the film formation process. Alternatively, the bias power supply 18 can alternately apply a negative bias voltage and a positive bias voltage to each of the plurality of substrate holders 16. The absolute value of the negative bias voltage is greater than the absolute value of the positive bias voltage.

[0023] If a negative bias voltage and a positive bias voltage are applied alternately, the bias power supply 18 may be, for example, an alternating current power supply (AC power supply) or a high frequency power supply (RF power supply).

[0024] The target 20 is a disk-shaped member made of yttrium. As an example, the target 20 is a disk having a diameter of 100 mm.

[0025] The arc power supply 22 is a DC power supply that functions as a discharge power supply to generate a vacuum arc discharge in the target 20 placed in the vacuum chamber 2. In this case, the target 20 functions as a cathode in the discharge. Meanwhile, as shown in FIG. 1, the vacuum chamber 12 functions as an anode in the discharge. The target 20 receives the discharge generated by the arc power supply 22 and emits ions of evaporated yttrium from its surface. The arc power supply 22, together with the target 20, constitutes an arc evaporation source.

[0026] The heater 24 is provided in the vacuum chamber 12 and generates heat when supplied with current from a heater power supply (not shown). As a result, the environment in the vacuum chamber 12 and the workpiece W are heated.

[0027] The argon tank 30 contains argon and supplies argon gas to the vacuum chamber 12. Similarly, the oxygen tank 32 contains oxygen and supplies oxygen to the vacuum chamber 12. The amount of gas supplied from these tanks is controlled by adjusting the opening of a regulator (not shown) in response to a command from the controller 50. In another embodiment, the amount of gas supplied may be manually adjusted by an operator.

[0028] The vacuum pump P creates a vacuum in the internal space of the vacuum chamber 12 through the exhaust port 12B (evacuation).

[0029] In addition to the regulators, the controller 50 controls the vacuum pump P, the bias power supply 18, the arc power supply 22, and various voltages or currents of the heater 24, as well as the rotation of the rotary table 14, etc.

[0030] Next, examples of the film forming method according to this embodiment will be described. In the following description, oxygen may be represented as O and yttrium as Y. The present invention is not limited to the scope of the following examples.

[0031] Example 1 The following describes Example 1. In carrying out the film formation method, as shown in Fig. 1, a target 20 and a workpiece W are attached to a film formation apparatus 10, and a vacuum chamber 12 is evacuated to a vacuum state by a vacuum pump P.

[0032] Next, after preheating inside the vacuum chamber 12 by the heater 24, argon gas is introduced from the argon tank 30 into the vacuum chamber 12 through the gas inlet 12A, and as a pretreatment, the surface of the workpiece W is bombarded with argon gas ions. Here, bombardment means that heavy inert gas ions such as argon ions are generated by plasma discharge, and these ions are irradiated onto the workpiece W to heat the surface of the workpiece W, thereby cleaning the surface.

[0033] After the above bombardment, pure oxygen gas is introduced at a flow rate of about 240 sccm so that the pressure in the chamber becomes about 1 Pa. In another embodiment, instead of pure oxygen gas, Ar—O ２ A mixed gas (e.g., Ar 450 sccm, oxygen 50 to 75 sccm) may be introduced so that the pressure inside the chamber becomes approximately 2 Pa. In order to maintain stable discharge, it is desirable to set the total pressure inside the chamber in the range of 0.6 Pa to 4 Pa.

[0034] Next, while the target 20 functions as a cathode, a discharge is generated in the vacuum chamber 12, and an yttrium oxide film is formed on the workpiece W. During this process, the temperature of the workpiece W is approximately 300°C (200°C to 400°C), the arc current is in the range of 100 A to 150 A, and the voltage applied to the workpiece W is a unipolar pulse with a frequency of 200 kHz, a duty of 56%, or 300 kHz, a duty of 60%, with the average voltage varied between 10 and 50 V. The thickness of the yttrium oxide film formed on the workpiece W is approximately 5 to 100 μm. As mentioned above, an example of the workpiece W is A6061Al (20 mm x 20 mm square piece). The amount of oxygen in the formed yttrium oxide film is controlled by changing the pressure of the oxygen flowing into the chamber, i.e., the oxygen partial pressure (oxygen flow rate).

[0035] Next, a method for evaluating the yttrium oxide film formed on the workpiece W will be described together with its indicators.

[0036] (1) O / Y ratio (ratio of oxygen to yttrium in the yttrium oxide film on the workpiece W) The formed test piece (workpiece W) was cut along the film thickness direction and embedded in a resin for evaluation. The cross section was polished, and then O and Y were measured at 10 points in the film from the cross-sectional direction using EDX (Energy Dispersive X-ray Spectroscopy), and the O / Y ratio was calculated from the average value.

[0037] (2) Electrical Resistance of Yttrium Oxide Film Electrodes were placed in contact with the back and front surfaces of the workpiece W (substrate), and a voltage (3.5 to 350 mV, varying depending on the resistance value) was applied between the electrodes. The electrical resistance of the film was calculated from the current value flowing at that time. A milliohm high tester (HIOKI 3540) was used for the measurement.

[0038] Figure 2 shows the electrical resistance of yttrium oxide films with different O / Y ratios. As mentioned above, the O / Y ratio was controlled by changing the oxygen partial pressure (oxygen flow rate) in the chamber. As shown in Figure 2, when the O / Y ratio of the yttrium oxide film becomes less than 1.4, the electrical resistance of the film drops sharply, confirming its conductivity. It is more desirable to set the O / Y ratio to 1.35 or less. In this case, the electrical resistance of the yttrium oxide film can be stably maintained at 10,000 Ω or less. In this measurement, the upper limit of the resistance value measured by the measuring device is 30,000 Ω, so all measurement points of 30,000 Ω in Figure 2 show electrical resistances above that value.

[0039] If a film is formed using oxygen alone and the oxygen flow rate is low, the pressure in the chamber will be low, the discharge voltage will increase, and the discharge will tend to become unstable. Therefore, Ar gas is further introduced into the chamber to form an Ar—O ２ As an example, when only 50 sccm of oxygen is introduced into the chamber and discharge is performed, the pressure in the chamber is 1×10 －２ In contrast, when 450 sccm of Ar gas and 50 sccm of oxygen gas were introduced and the chamber pressure was set to 2.5 Pa, the discharge voltage was low at around 17 V, and a stable discharge could be maintained. It is more preferable to introduce Ar so that the chamber pressure during discharge is 1 Pa or higher.

[0040] In the present invention, the yttrium oxide film is a film containing Y ２ O ３ and Y are mixed together, and Y ２ O ３ As a result of changing the ratio of Y to O in the film, the ratio of Y to O in the film changes. ２ O ３ The film in which Y and O are mixed together is collectively referred to as an "yttrium oxide film." Note that the ratio of Y to O in this case is an atomic ratio. As an example, the thickness of the yttrium oxide film on the workpiece W is 50 μm or more.

[0041] Example 2 Next, Example 2 will be described. In Example 2, a target 20 (100 mm in diameter) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus ( FIG. 1 ) connected to an arc power supply 22 consisting of a DC power supply. After evacuation and preheating, argon gas was introduced into the vacuum chamber 2 at 150 sccm or 450 sccm. The pressure (total pressure) inside the vacuum chamber 2 was adjusted to approximately 1 to 2 Pa. Pure oxygen gas was then introduced at a constant rate (e.g., 45 sccm), and the arc evaporation source was allowed to discharge for 5 minutes at a current of 100 A or more but not exceeding 150 A. The change in discharge voltage was then measured. The amount of oxygen in the vacuum chamber 2 was then increased, and the process of discharging for another 5 minutes was repeated until the oxygen flow rate reached a point where the discharge voltage rose sharply.

[0042] 3 is a graph showing the relationship between the flow rate of oxygen introduced into the vacuum chamber 2 and the oxygen partial pressure in Example 2. The oxygen partial pressure was calculated by multiplying the total pressure in the vacuum chamber 2 measured with a diaphragm pressure gauge (manufactured by MKS) by the oxygen flow rate and then dividing the result by the total gas flow rate (argon + oxygen). As shown in FIG. 3, it can be seen that the oxygen partial pressure changes almost linearly with the oxygen flow rate.

[0043] 4 and 5 are graphs showing the relationship between oxygen partial pressure and discharge voltage in Example 2. Fig. 4 shows the results when the arc current was 100 A, and Fig. 5 shows the results when the arc current was 150 A. Both Fig. 4 and Fig. 5 show experiments with two levels of argon gas introduction amount (150 sccm and 450 sccm).

[0044] 4 and 5, it can be seen that the discharge voltage increases with the oxygen partial pressure, and that the increase in discharge voltage relative to an increase in oxygen partial pressure becomes rapid between 0.3 and 0.4 Pa. From the perspective of discharge voltage, this phenomenon indicates that a discharge voltage of 20 V or less is desirable in the system used in this experiment. From this, it was discovered that in order to maintain a stable discharge during film formation, it is necessary to control the oxygen partial pressure in the vacuum chamber 2 to less than 0.4 Pa at most.

[0045] Example 3 Next, Example 3 will be described. In Example 3, a target 20 (diameter 100 mm) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus (FIG. 1) connected to an arc power supply 22 consisting of a DC power supply. After evacuation and preheating, 150 sccm of argon gas was introduced into the vacuum chamber 2. At this time, the pressure (total pressure) in the vacuum chamber 2 was approximately 2 Pa. Pure oxygen gas was then introduced, and the arc evaporation source was discharged with a current of 125 A to form an yttrium oxide film on a Si substrate (workpiece W) with a target thickness of 3 μm. A pulse bias (voltage -10 V, frequency 200 kHz, pulse width 2.8 μS) was applied during film formation. The surface roughness (Ra) of the formed film was measured using a stylus-type surface roughness meter (Tokyo Seimitsu SURFCOM TOUCH550).

[0046] 6 is a graph showing the surface roughness of yttrium oxide films formed by varying the oxygen partial pressure in Example 3. As shown in FIG. 6, the surface roughness increases with decreasing oxygen partial pressure. Since increasing the surface roughness requires polishing or other processes in practical use, it is desirable for the surface roughness to be 0.4 μm or less. Therefore, it is desirable to set the lower limit of the oxygen partial pressure (x) to 0.17 Pa, which is obtained by substituting Ra(y) = 0.4 into the regression equation (y = -1.7628x + 0.6961) based on the results of FIG. 6. Thus, it is desirable to set the oxygen partial pressure during film formation to 0.17 Pa or higher.

[0047] Example 4 Next, Example 4 will be described. In Example 4, a target 20 (diameter 100 mm) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus ( FIG. 1 ) connected to an arc power supply 22 consisting of a DC power supply. After evacuation and preheating, 450 sccm of argon gas was introduced into the vacuum chamber 2. At this time, the introduction was performed so that the pressure (total pressure) in the vacuum chamber 2 was approximately 2 Pa. Thereafter, 50 sccm of pure oxygen gas was introduced, and the arc evaporation source was discharged at a current of 100 A for 400 minutes, and the changes in the oxygen partial pressure and discharge voltage in the vacuum chamber 2 were measured.

[0048] Fig. 7 is a graph showing the change in oxygen partial pressure during long-term discharge in Example 4. Fig. 8 is a graph showing the change in discharge voltage during long-term discharge in Example 4.

[0049] 7 and 8, it can be seen that by controlling the oxygen partial pressure in the vacuum chamber 2 to less than 0.4 Pa, the discharge voltage was stabilized (20 V or less), and long-term discharge became possible. Note that the above-mentioned Examples 2 and 4 were intended to evaluate the discharge characteristics, and no actual film formation was performed.

[0050] As described above, when the discharge current (arc current) is in the range of 100 A or more and 150 A or less and the amount of argon gas introduced is in the range of 150 sccm or more and 450 sccm or less, by adjusting the oxygen partial pressure in the vacuum chamber 2 to a range of less than 0.4 Pa, it is possible to maintain a stable discharge.

[0051] Example 5 Next, Example 5 will be described. In Example 5, a target 20 (diameter 100 mm) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus ( FIG. 1 ) connected to an arc power supply 22 consisting of a DC power supply. After evacuation and preheating, the target was bombarded with argon gas ions. After this gas bombardment, pure oxygen gas was introduced into the vacuum chamber 2 at a pressure of about 1 Pa and a flow rate of about 240 sccm, or a mixed gas of argon and pure oxygen (Ar 450 sccm, oxygen 50 to 75 sccm) so that the total pressure was about 2 Pa. Then, a discharge was caused using the metal Y target 20 as a cathode, and an yttrium oxide film was formed on the workpiece W. The temperature of the workpiece W during film formation was around 300°C, the arc current was between 100 and 150 A, and the voltage applied to the workpiece W was a unipolar pulse with a frequency of 200 kHz, a duty of 56% or 300 kHz, a duty of 60%, with an average voltage varied between 10 and 50 V. The thickness of the formed film was approximately 5 to 100 μm. A6061Al (20 x 20 square) was used as the substrate for the workpiece W. The amount of oxygen in the yttrium oxide film was controlled by changing the oxygen partial pressure (oxygen flow rate) in the vacuum chamber 2.

[0052] 9 is a graph showing the O / Y ratio of yttrium oxide films formed by changing the oxygen partial pressure in Example 5. The method for calculating the O / Y ratio is the same as that described above. As shown in FIG. 9, it can be confirmed that the O / Y ratio of yttrium oxide films formed at an oxygen partial pressure of less than 0.4 Pa is 1.5 or less (1.51 or less).

[0053] The embodiments of the present invention have been described above in detail. The yttrium oxide film obtained by the film formation method according to the present invention can be widely applied to members exposed to plasma, such as semiconductor manufacturing equipment. In particular, by forming an yttrium oxide film by the arc ion plating method, it is possible to form a film that is denser and more plasma-resistant than when formed by a thermal spraying method.

[0054] The film formation method according to the present invention is a film formation method for forming an yttrium oxide film on a substrate, which is the object of the film formation, by an arc ion plating method, and includes the steps of placing a target 20 made of yttrium and a workpiece W (substrate) in a vacuum chamber 2, introducing at least oxygen into the vacuum chamber 2, applying a predetermined bias voltage to the workpiece W, evaporating the surface of the target 20 in the oxygen to form an yttrium oxide film on the workpiece W, and setting the oxygen partial pressure in the vacuum chamber 2 during the evaporation to a pressure less than 0.4 Pa such that the O / Y ratio, which is the ratio of oxygen to yttrium in the yttrium oxide film on the workpiece W, is 1.5 or less.

[0055] According to this film formation method, the amount of oxygen in the yttrium oxide film is changed by controlling the oxygen partial pressure in the vacuum chamber 2 during film formation, thereby reducing the electrical resistance of the film and obtaining a conductive yttrium oxide film. In particular, because the oxygen partial pressure is set to less than 0.4 Pa, oxides are less likely to form on the surface of the target 20, and it is possible to prevent an increase in discharge voltage that makes it difficult to sustain discharge.

[0056] The above method preferably further comprises setting the oxygen partial pressure in the vacuum chamber 2 during the evaporation so that the O / Y ratio is less than 1.4. This method further reduces the electrical resistance of the film, making it possible to stably obtain a conductive yttrium oxide film.

[0057] In the above method, it is preferable to further include setting the oxygen partial pressure in the vacuum chamber 2 so that the electrical resistance of the yttrium oxide film is 10,000 Ω or less. According to this method, by controlling the oxygen partial pressure during film formation to change the amount of oxygen in the film, it is possible to stably obtain a conductive yttrium oxide film having an electrical resistance of 10,000 Ω or less.

[0058] In the above method, it is preferable to further include setting the oxygen partial pressure so that the discharge voltage during film formation is not more than 20 V. According to this method, the oxygen partial pressure can be used to suppress an increase in the rate of increase in discharge voltage caused by an increase in discharge voltage, thereby making it possible to maintain stable discharge during film formation.

[0059] In the above method, it is preferable that the oxygen partial pressure is equal to or greater than 0.17 Pa. According to this method, it is possible to prevent the roughness of the formed film from increasing in accordance with a decrease in the oxygen partial pressure.

[0060] In the above method, it is desirable to further include introducing argon in addition to oxygen into the vacuum chamber 2. According to this method, it is possible to reduce the discharge voltage during film formation, and to stabilize the discharge during film formation.

[0061] The above method preferably further comprises applying a pulse voltage as the bias voltage to the workpiece W. According to this method, even if the resistance of the coating formed on the workpiece W is relatively high, charge-up caused by the incident ions can be suppressed.

[0062] It is desirable to obtain the yttrium oxide film having a high electrical resistance with an O / Y ratio of 1.4 to 1.5. In this case, as described above, by setting the oxygen partial pressure in the vacuum chamber 2 to a pressure of less than 0.4 Pa so that the O / Y ratio of the yttrium oxide film is 1.5 or less, excellent discharge stability can be obtained.

[0063] Furthermore, if the oxygen flow rate (oxygen partial pressure) is high during film formation, oxides are formed on the surface of the metal target 20, which increases the discharge voltage and makes it difficult to sustain the discharge. As in the previous example, the rate of increase in discharge voltage tends to increase as the discharge voltage increases, so it is desirable to adjust the oxygen flow rate (oxygen partial pressure) so that the discharge voltage is 20 V or less, more preferably 18 V or less. Furthermore, since the roughness of the formed film increases as the oxygen partial pressure in the vacuum chamber 2 decreases, it is preferable to set the oxygen partial pressure to 0.17 Pa or more.

[0064] It should be noted that these are merely examples, and the present invention should not be construed as being limited in any way by the description of the above-mentioned embodiments. In the present invention, the substrate is not limited to one made of an insulating material, and may be made of a conductive material. In the present invention, the mode in which the negative bias voltage and the positive bias voltage are alternately applied is not limited to the pulsed form described in the above-mentioned embodiments, and may be, for example, a sinusoidal wave form. Furthermore, if the arc current is too small, the discharge will not be stable, and if it is too large, the target may be heated. Therefore, for a target with a diameter of about 100 mm, it is desirable to set the arc current in the range of 50 A or more and 200 A or less.

[0065] A film formation method according to the present invention is a film formation method for forming an yttrium oxide film on a substrate, which is the object of film formation, by an arc ion plating method, and includes the steps of: placing a target made of yttrium and the substrate in a chamber; introducing at least oxygen into the chamber; applying a predetermined bias voltage to the substrate; evaporating the surface of the target in oxygen to form an yttrium oxide film on the substrate; and setting the oxygen partial pressure in the chamber during the evaporation to a pressure less than 0.4 Pa such that the O / Y ratio, which is the ratio of oxygen to yttrium in the yttrium oxide film on the substrate, is 1.5 or less.

[0066] According to this method, by controlling the oxygen partial pressure in the chamber during film formation to change the amount of oxygen in the yttrium oxide film, it is possible to reduce the electrical resistance of the film and obtain a conductive yttrium oxide film. In particular, because the oxygen partial pressure is set to less than 0.4 Pa, oxides are less likely to form on the target surface, and it is possible to prevent an increase in discharge voltage that makes it difficult to sustain discharge.

[0067] The above method may further comprise setting the oxygen partial pressure in the chamber during the evaporation so that the O / Y ratio is less than 1.4.

[0068] According to this method, the electrical resistance of the film can be further reduced, and an electrically conductive yttrium oxide film can be stably obtained.

[0069] The above method may further comprise setting an oxygen partial pressure in the chamber so that the electrical resistance of the yttrium oxide film is 10,000 Ω or less.

[0070] According to this method, by controlling the oxygen partial pressure during film formation to change the amount of oxygen in the film, it is possible to stably obtain a conductive yttrium oxide film having an electrical resistance of 10,000 Ω or less.

[0071] The above method may further comprise setting the oxygen partial pressure so that a discharge voltage during film formation is 20 V or less.

[0072] According to this method, the increase in the rate of increase in the discharge voltage due to an increase in the discharge voltage can be suppressed by adjusting the oxygen partial pressure, and stable discharge can be maintained during film formation.

[0073] The above method may further include setting the oxygen partial pressure to 0.17 Pa or higher.

[0074] According to this method, it is possible to prevent the roughness of the formed film from increasing in accordance with a decrease in the oxygen partial pressure.

[0075] The above method may further comprise introducing argon into the chamber in addition to oxygen.

[0076] According to this method, it is possible to lower the discharge voltage during film formation, and to stabilize the discharge during film formation.

[0077] The above method may further comprise applying a pulse voltage to the substrate as the bias voltage.

[0078] According to this method, even if the resistance of the film formed on the substrate is relatively high, charge buildup caused by incident ions can be suppressed.

[0079] According to the present invention, it is possible to provide a film formation method that can stably maintain discharge during film formation when stably forming an electrically conductive yttrium oxide film on a substrate using an arc ion plating method.

Claims

1. A method for forming an yttrium oxide film on a substrate by an arc ion plating method, the method comprising: placing a target made of yttrium and the substrate in a chamber; introducing at least oxygen into the chamber; applying a predetermined bias voltage to the substrate; evaporating the surface of the target in oxygen to form an yttrium oxide film on the substrate; and setting the oxygen partial pressure in the chamber during the evaporation to a pressure less than 0.4 Pa such that the O / Y ratio, which is the ratio of oxygen to yttrium in the yttrium oxide film on the substrate, is 1.5 or less.

2. A method for forming an yttrium oxide film as set forth in claim 1, further comprising setting the oxygen partial pressure in said chamber during said evaporation so that said O / Y ratio is less than 1.

4.

3. A method for forming an yttrium oxide film according to claim 2, further comprising setting the oxygen partial pressure in the chamber so that the electrical resistance of the yttrium oxide film is 10,000 Ω or less.

4. The method for forming an yttrium oxide film according to claim 1, further comprising setting the oxygen partial pressure so that a discharge voltage during film formation is 20 V or less.

5. The method for forming an yttrium oxide film according to claim 1, further comprising the step of: setting the oxygen partial pressure to 0.17 Pa or more.

6. A method for forming an yttrium oxide film according to any one of claims 1 to 5, further comprising introducing argon into the chamber in addition to oxygen.

7. A method for forming an yttrium oxide film according to any one of claims 1 to 5, further comprising applying a pulse voltage to the substrate as the bias voltage.

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